Open Hearth Process

The open hearth furnace consists of a big brick room with a low
arched roof. It is charged with pig iron and scrap through doors
in the side walls.

Through openings at one end of the furnace come hot air and gas,
which burn in the furnace, producing sufficient heat to melt the
charge and refine it of its impurities. Lime and other nonmetallic
substances are put in the furnace. These melt, forming a slag
which floats on the metal and aids materially in the refining
operations.

In the bessemer process air is forced through the metal. In the
open-hearth furnace the metal is protected from the flaming gases
by a slag covering. Therefore it is reasonable to suppose that
the final product will not contain so much gas.

A diagram of a modern regenerative furnace is shown in Fig. 3.
Air and gas enter the hearth through chambers loosely packed with
hot fire brick, burn, and exit to the chimney through another pair
of chambers, giving to them some of the heat which would otherwise
waste. The direction is reversed about every twenty minutes by
changing the position of the dampers.